Means for coating sheet material



June 25, 1963 G. H. DALsEMER Erm. 3,095,327

MEANS FOR coATING SHEET MATERIAL MWMMJ Filed NOV. 5, 1959 June 25, 1963 G. H. IIDALSEMER El' AL MEANS FOR COATING SHEET MATERIAL 2 Sheets-Sheet 2 Filed Nov. 5, 1959 INVENTOR. Gooo/v @Awe/vc@ BY MURRAY BIA/Fox ,4rrOp/vev United States The present invention relates to an apparatus for coating sheet material and more particularly to a method and apparatus for providing a high-gloss coating on sheet material such as paperboard carton blanks, cards, and similar articles.

Coatings have long been applied to paper and paperboard in the packaging field to improve their sealing properties by making them relatively air-tight and moisture resistant. Petroleum wax such as crystalline paraffin is commonly used for this purpose. Various other waxes such as amorphous or microcrystalline wax have been added to improve the characteristics of the coatings -and to make them more flexible and more adherent. Also plastics such as polyethylene have lbeen added to the coating compositions to further improve both the sealing characteristics and appearance or gloss of the coated articles. Different compositions depend on the temperature and the use to which they are likely to be subjected. Thus, different c-oating compositions are used from time to time in different runs on the same coating machines and on generally similar products. This means that the coating method and apparatus should be adaptable to provide the protective coating and the necessary gloss even though substantial variations are made in the coating compositions.

The present invention provides a new and improved apparatus for forming an improved high-gloss .coating which is useful with a wide variety of compositions, thus giving a greater choice of lcoating without changing the method or the machine. Present methods require certain adhesion values and other limitations on the coatings which are a handicap in both the choice of coating and the application of it.

In applying low gloss coatings the coating method known in the trade as cold waxing is fused wherein the sheets are fed first through a wax applying device and then through a cold water bath so that the wax is first applied and then hardened on the paperboard surfaces. Such cold water waxing including the use of baths has not proved satisfactory, however, where a high-gloss finish is desirable on the sheets.

High-gloss finishes with the wax type coating compositions have been obtained through the use of casting surfaces. These yare highly polished surfaces with mirrorlike finishes onto which the coated sheets are pressed while the coating is `still in a semi-liquid or plastic state. The coatings are permitted to harden in contact with the glossy surface and the sheets are thereafter stripped from the surface so that they retain a glossy sheen corresponding to that of the casting surface. Such a casting means is disclosed in the Corbin Patent No. 2,270,038. In the case of wax coating containing ingredients such as parahin, microcrystalline wax, and polyethylene serious difficulty arises in removing the coated sheets from the casting surface without impairing the gloss.

The present invention provides a new combination ,of a casting surface and a removal means which overcomes prior diiliculties and which widens the range of coating compositions usable. The invention also provides an improved high speed and more efficient glossing operation.

An object of the present invention is to provide an `improved high-gloss coating machine which may be arent operated at high speed to provide a high-gloss coating in which the coated articles are rapidly removed Without impairing the gloss.

Another object of the present invention is to provide a high-gloss waxing means Vapplicable to a wide range of coating compositions.

Another object of the present invention is to provide a Ahigh-gloss waxing machine which operates at high speeds through the combination of high speed wax applicators with high speed glossing and take-off apparatus.

Another object of the present invention is to provide an improved means for removing coated sheets from a casting surface.

Other and further `objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described or will be indicated in the appended claims7 and various advantages not referred to herein will occur to one skilled in the art upon ernployment of the invention in practice.

A preferred embodiment of the invention has been chosen for purposes of illustration and description and is shown in the accompanying drawings, forming a part of the specification, wherein:

FIG. l is a side elevational view of a high-gloss coating machine including the preferred embodiment of the vacuum take-off apparatus according to the present invention;

FIG. 2 is a fragmentary enlarged detailed view of the coating apparatus of FIG. l illustrating the preferred embodiment of the vacuum take-off;

FIG. 3 is a top plan view of the vacuum take-off of PEG. 2 partially broken away; and

FIG. 4 is a sectional view of the vacuum take-off taken along line 4 4 of FIG. 2.

The waxing apparatus will first be described generally with particular reference to FIG. l, which illustrates a preferred embodiment of applicants high-gloss waxing apparatus particularly adapted for the coating of paperboard sheets. A feeder 1 which may be 1any of the usual types of sheet feeding devices, feeds one or more stacks 3 of sheets continuously into a wax applicator illustrated at 4. The wax `'applicators 4 also may be any of the commercially ,available Wax applicators although preferably it is chosen to have a high waxing capacity so that it may wax one or more rows of sheets 2 land feed the-m onto a glossing means .indicated generally iat 5. The waxing applicator 4 comprises a wax formulation reservoir 6 in which the wax formulation is retained at 4a temperature sufficiently high to melt the wax formulation. Sheets 2 pass between a set -of upper rollers 7 and -a set of lower rollers 8 4as the lower rollers S transfer a coating of the wax formulation from the reservoir 6 to the lower surface of the sheets 2. The applicator 4 passes the sheets 2 ywith their lower surfaces coated with a liquid or plastic coating onto a highly polished casting belt 9. The sheets 2 are yfirmly pressed or cast onto the belt 5 while the coating is still in a plastic state by resilient pressure roller 16u Preferably an 'additional steel roller 1I is mounted above `and in contact with the casting lroller 10. A thermostatically controlled heater may be provided in roller liti to prevent premature hardening of the coating formulations -on the sheets 2. The sheets 2 should be pressed `against the belt 9 while the coating on their lower surface is in a liquid or plastic state. The upper roller `1'1 is provided with ia doctor blade l2 which removes any eX- cess coating material transferred from the tops of the sheets 2 to the pressure roller ll!) and thence to the steel roller 11. The waxing rollers 7 and 8 are steel rollers.

The casting belt 9 may be made of stainless steel with a highly polished outer surface `adapted to cast the coating on the sheets 2 and to provide a mirror-like finish as the coating hardens in contact with the polished belt surface.

9 In order to expedite `the hardening of the coating the belt 9 preferably has its upper run 13 water cooled.

Any suitable cooling means may be utilized but the preferred embodiment comprises a tray i4 within a larger tray 115 under it. 'Ille tray 14 is supplied with sufficient water so that it overflows with the tray below it receiving the overllow. The underside of the upper strand of the belt 9 is cooled by passing over the surface of the liquid in contact with it. Other means such as sprays may be used, if desired. The steel casting belt 9 is mounted on end pulleys 16 and 17, one or both of which may be suitably driven.

The belt 9 carries the coated sheets 2 pressed on its upper surface above the water cooler 14 to harden the coating. We have discovered that when the sheets are left `on the belt 9 for a sufliciently long period the soliditica- Ition of the coating 1in the hardening process causes the sheets to lift or free themselves at least partially from the belt. We have also found that a relatively long belt run is needed to cause the sheets to free themselves before they reach the end of the upper run of the belt. In the preferred embodiment the belt 9 has `an upper run of about 25 to 30 feet to permit disengagement of cartons having a wide range of coating compositions. Preferably the belt is kept at about 75 F. for runs at speeds of 300 to 500` feet a minute.

As will be more fully described below, the vacuum take-olf device 18 provides a lifting force which lifts each of the sheets 2 clear of the belt 9 before the sheets reach the end of the upper run. The vacuum take-off device 18 thereafter transfers the sheets 2 to a separate removal belt 19.

As noted above it has been discovered that a relatively long belt 9 provides for a hardening of the coatings to the point where the coated sheets 2 lift or draw at least partially clear of the surface of the belt 9. This characteristic of the sheets to lift free of the belt is aided by the natural tendencies of the coated sheets 2 to curl slightly as the coatings harden. In order to provide for a rapid, orderly, and certain removal of all of the sheets from the belt surface and to complete the freeing of the sheets in some cases the vacuum take-olf means 13 is provided to create a lifting force which eounteracts any tendencies of the sheets 2 to adhere to the upper surface of the belt and which lifts the cartons upwardly and clear of the belt 9.

A preferred embodiment of the vacuum take-off 1S is illustrated in detail in FIGS. 2-4. The vacuum take-off 18 comprises a hollow vacuum chamber 20 having a bottom 21 serving `as Ia belt guide. A conveyor belt 22 is mounted on suitable end pulleys 2li and 25 with its lower run 26 against the bottom 21 of the vacuum chamber and spaced `about one inch above the surface of the casting belt 9. A suitable vacuum pump .is connected to the outlet 27 `of the vacuum chamber 20 to form a vacuum therein. The lower run 26 of the belt 22 and the upper surface of the casting belt 9 and the sheets 2 thereon are subjected to an upward attraction by the provision of suitable slots 28 in the bottom of the chamber 2t). In its preferred embodiment the conveyor 22 is provided with spaced apertures 29 as illustrated in FIGS. 3 and 4. These apertures 29 are positioned to coincide with the slots 23 to permit -air to` be drawn into the vacuum chamber through the apertures 29 and slots 2S so :that the vacuum lifts the sheets 2 clear of the upper surface of the casting belt 9 as illustrated by the raised cartons 2a `and 2b in FIG. 2. One or both of the end pulleys 24 `and 25 are driven to move the take-olf belt 22 at the same speed as the casting belt 9.

The bottom 21 of the vacuum chamber 26 extends beyond the casting belt 9 and over the belt i9 which receives the coated blanks and takes them from the machine. At the end of the vacuum chamber, there is provided a conduit or pipe 31 extending across the outer end of the chamber and enclosed by a member 23 extending down to the lower strand of the conveyor belt 22. The application of pressure over the perforated belt at this point prevents any of the blanks from adhering to the belt after the belt passes the vacuum chamber. In all probability, the sheet would drop off, but the pressure zone over the belt immediately after it leaves the vacuum chamber assures that result.

In the preferred embodiment, a silicone oil is applied to the surface of the casting belt 9 prior to the application of the sheets 2 onto the belt. The oil serves as a lubricant which facilitates the separation of the cast surface from the stainless steel belt without damaging the high-gloss of the coating. Preferably the silicone oil is continuously applied to the belt 9 by the applicators shown generally at 32 which may comprise a reservoir 33 and a roller 34 extending into the oil with a transfer roller 35 engaging it for transfer of the thin coating of the oil to the belt.

Preferably the conveyor, the wax applicator, the casting belt, the vacuum removal belt 18, and the carton removal belt 19 are interconnected to drive the sheets at the same speed.

It will be seen that the present invention provides an improved apparatus for applying a high-gloss coating which may be utilized with a wide range of wax compositions. By having the wax coating in contact with the casting surface until the coating releases itself from the surface, a higher gloss is obtained. Where the articles are pulled from the casting surface while there is substantial adhesion to the surface, there is a tendency to impair the sheen. The improved vacuum take-off which is positioned about one inch above the blanks on the casting belt raises tee blanks directly off the belt. Since the two belts are moving at the same speed, there is no tendency for slippage between the casting belt and the blanks. In addition, the take-off carries the blanks with the highgloss surface exposed to cooling air for a period which permits further hardening of the surface prior to their being deposited onto a conveyor for transfer to a packing station. Thus, the surface is protected until it hardens suiciently to withstand surface contacts with other blanks. If desired, the blanks could be delivered with the high-gloss surface up but -that has not been found to be necessary. By reason of the improvements, higher speeds may be utilized and lower costs with better quality achieved.

As various changes may be made in the form, construction and arrangement of the parts herein without departing from the spirit and scope of the invention and without sacrificing any of its advantages, it is to be understood that all matter herein is to be interpreted as illustrative and not in a limiting sense.

Having thus described our invention, we claim:

l. In a coating machine of the class in which a succession of paperboard blanks have a. thermo-plastic coating applied to one surface thereof and said coated blanks are then pressed against an elongated run of a casting belt with the coated surface of the blanks against the smooth surface of 'the belt and adhered thereto and a cooling means is applied to said run for hardening the thermo-plastic coating, the combination with said run of a permeable conveyor belt positioned adjacent to the terminal portion of the elongated run of said casting belt and spaced outwardly of the casting belt, means to move said conveyor belt at about the speed of the casting belt, vacuum means at said conveyor belt for transferring the blanks from the casting belt to said conveyor belt and for retaining the blanks on the conveyor belt with the coated surfaces of the blanks continuously spaced from the casting belt, and means lfor thereafter removing the blanks from the conveyor belt.

2. In a coating machine of the class in which a succession of paperboard blanks have a thermo-plastic coating applied to one surface thereof and said coated blanks are then pressed against a straight run of a casting belt with the coated surface 0f `the blanks against the smooth surface of the belt and adhered thereto and a cooling means is applied to `said run for hardening the thermoplastic coating, the combination with said run of a permeable conveyor belt juxtaposed in spaced relation to the terminal portion of the straight run of said casting belt and spaced a distance greater than one blank thickness outwardly of the casting belt, means to move said conveyor belt at about the speed of the casting belt, vacuum means at said conveyor belt for transferring the blanks from the casting belt to said conveyor belt and for retaining the lblanks on the conveyor belt with the coated surfaces of the blanks continuously spaced from the casting belt, and means for thereafter removing the blanks from the conveyor belt.

3. In a coating machine of the class in which a succession of paperboard blanks have a thermo-plastic coating applied to one surface thereof and said coated blanks are then pressed against a straight run of a casting belt with lthe coated surface of the blanks against the smooth surface of the belt and adhered thereto and a cooling means is applied to said run for hardening the thermoplastic coating, the combination with said run of a permeable conveyor belt having an elongated relatively straight run extending along the terminal portion of the straight run of said casting belt and spaced outwardly of the casting belt, means to move said conveyor bel-t at about the speed of the casting belt, vacuum chamber means extending along a substantial portion of said elongated conveyor means -for transferring the blanks from the casting belt to said conveyor belt and for retaining 30 2,892,735

the blanks on the conveyor belt lwith the coated surfaces of the blanks continuously spaced from the casting belt, and means for thereafter removing the blanks from the conveyor belt.

4. In a coating machine of the class in which a succession of paperboard blanlcs have a thermo-plastic coating applied to one surface thereof and said coated blanks are then pressed against a straight run of a casting belt with the coated `surface of the blanks against the smooth surface of the belt and adhered thereto and a cooling means is applied to said -run for hardening the thermoplastic coating, the combination lwith said run of a permeable conveyor belt having an elongated relatively straight run extending along the terminal portion of the straight run of said casting belt and spaced a distance greater than `one blank thickness outwardly of the casting belt, means to move lsaid conveyor belt at about the speed of the casting belt, vacuum chamber means extending along a substantial portion of said elongated conveyor |belt inn for transferring the blanks from the casting belt to said conveyor belt and for retaining the blanks on the conveyor belt with the coated surfaces of the blanks continuously spaced from the casting belt, blank stacking means adjacent said conveyor belt and beyond said vacuum chamber means ttor receiving blanks released from -said conveyor belt, and blank releasing means adjacent said conveyor belt and :beyond said vacuum chamber means.

References Cited in the tile of this patent UNITED STATES PATENTS 2,526,318 Battin Oct. 17, 1950 Curler et al. June 30, 1959 FOREIGN PATENTS 201,776 France Nov. 7, 1889 

1. IN A COATING MACHINE OF THE CLASS IN WHICH A SUCCESSION OF PAPERBOARD BLANKS HAVE A THERMO-PLASTIC COATING APPLIED TO ONE SURFACE THEREOF AND SAID COATED BLANKS ARE THEN PRESSED AGAINST AN ELONGATED RUN OF A CASTING BELT WITH THE COATED SURFACE OF THE BLANKS AGAINST THE SMOOTH SURFACE OF THE BELT AND ADHERED THERETO AND A COOLING MEANS IS APPLIED TO SAID RUN FOR HARDENING THE THERMO-PLASTIC COATING, THE COMBINATION WITH SAID RUN OF A PERMEABLE CONVEYOR BELT POSITIONED ADJACENT TO THE TERMINAL PORTION OF THE ELONGATED RUN OF SAID CASTING BELT AND SPACED OUTWARDLY OF THE CASTING BELT, MEANS TO MOVE SAID CONVEYOR BELT AT ABOUT THE SPEED OF THE CASTING BELT, VACUUM MEANS AT SAID CONVEYOR BELT FOR TRANSFERRING THE BLANKS FROM THE CASTING BELT TO SAID CONVEYOR BELT AND FOR RETAINING THE BLANKS ON THE CONVEYOR BELT WITH THE COATED SURFACES OF THE BLANKS CONTINUOUSLY SPACED FROM THE CASTING BELT, AND MEANS FOR THEREAFTER REMOVING THE BLANKS FROM THE CONVEYOR BELT. 